Littérature scientifique sur le sujet « Latitudes subtropicales »
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Consultez les listes thématiques d’articles de revues, de livres, de thèses, de rapports de conférences et d’autres sources académiques sur le sujet « Latitudes subtropicales ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Articles de revues sur le sujet "Latitudes subtropicales"
1
Poblete, Arnobio Germán, et Juan Leonidas Minetti. « Propuesta de un índice de sequía para valuar la posible expansión de la celda de Hadley y su relación con la crisis hídrica de las regiones subtropicales del hemisferio sur ». Geográfica digital 12, no 24 (24 octobre 2017) : 1. http://dx.doi.org/10.30972/geo.12242158.
Texte intégralRésumé :
<p>La celda de Hadley (HC) es la más importante de la circulación general atmosférica por su rol fundamental en el sistema climático, y por ende su impacto sobre el clima global. Sus principales componentes son: La Convergencia Intertropical de la circulación en superficie -alisios- (ITCZ) con el</p><p>consiguiente ascenso, condensación y posible precipitación; y la circulación de altura formada por los Contralisios subsidentes (CAS) en las regiones subtropicales de ambos hemisferios, provocando calentamiento y secamiento del aire descendente, con el consiguiente aumento de masa.</p><p>Recientemente se ha puesto especial énfasis en los cambios latitudinales de la ITCZ y CAS posiblemente como resultado de un proceso de expansión de la HC producido por el calentamiento global (CG). Esta intensificación/debilitamiento de la HC a su vez está asociada/o con el crecimiento/disminución de las precipitaciones en la ITCZ y disminución/crecimiento de las precipitaciones en la banda subtropical, contribuyendo al incremento de las frecuencias de sequías en</p><p>latitudes medias de ambos hemisferios. En ese marco, se buscó una explicación sobre la intensificación y desplazamiento hacia altas latitudes de la posición del anticiclón subtropical del Pacífico Sur (LSAP).</p><p>Para comprobar el impacto descripto del CG sobre la celda de Hadley y de esta en la subsidencia sobre los anticiclones subtropicales del Hemisferio Sur (HS), se construye un índice de sequía hemisférico, con el objeto de relacionarlo con las principales variables asociadas a los procesos precipitantes en el mismo, y de esa manera contextualizar la crisis hídrica que están soportando dichas regiones.</p><p> </p>
2
Dorta Antequera, Pedro. « Las inversiones térmicas en Canarias ». Investigaciones Geográficas, no 15 (15 juin 1996) : 109. http://dx.doi.org/10.14198/ingeo1996.15.01.
Texte intégralRésumé :
La localización geográfica del archipiélago canario, en latitudes subtropicales y con un predominio casi absoluto de los vientos alisios, determina una estructura vertical de la baja troposfera con una presencia constante de inversiones térmicas, de subsidencia en la mayor parte de los casos, que explican la fuerte tendencia a la estabilidad de toda esta región. Realizar un primer análisis estadístico de estas inversiones así como estudiar su origen supone el tema de estudio de este trabajo.
3
Antonio Arz, José, et Eustoquio Molina. « Late Campanian and Maastrichtian bitostratigraphy based on planctonic foraminifera from temperate to subtropical latitudes (Spain, France and Tunisia) ». Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 224, no 2 (24 mai 2002) : 161–95. http://dx.doi.org/10.1127/njgpa/224/2002/161.
Texte intégral
4
LEBOEUF, B., J. A. DELGADILLO, E. MANFREDI, A. PIACERE, V. CLEMENT, P. MARTIN, M. T. PELLICER-RUBIO, P. BOUÉ et R. DE CREMOUX. « Place de la maîtrise de la reproduction dans les schémas de sélection en chèvres laitières ». INRAE Productions Animales 21, no 5 (27 novembre 2008) : 391–402. http://dx.doi.org/10.20870/productions-animales.2008.21.5.3414.
Texte intégralRésumé :
La saisonnalité de la reproduction chez les chèvres originaires des latitudes tempérées ou subtropicales peut maintenant être contrôlée par des changements artificiels de la photopériode. Les jours courts stimulent l’activité sexuelle tandis que les jours longs l’inhibent. Ces connaissances ont permis le développement de traitements photopériodiques pour le contrôle de l’activité sexuelle des chèvres et des boucs.
En France, l’Insémination Artificielle (IA) des chèvres joue un rôle central pour le contrôle des appariements et l’organisation du schéma de sélection. La plupart des chèvres sont inséminées en dehors de la saison sexuelle avec de la semence cryoconservée, après induction hormonale de l’ovulation seule ou en combinaison avec des traitements photopériodiques. Les taux de fertilité sont en moyenne de 65%. De nouvelles stratégies sont en cours d’expérimentation. Elles sont basées sur l’IA après un effet mâle pour réduire l’utilisation des hormones.
Le schéma de sélection s’est développé grâce aux progrès de l’IA. Ce schéma repose sur des plans d’accouplements entre reproducteurs d’élite, le testage sur descendance en fermes et la diffusion des semences de boucs améliorateurs. Après les caractères laitiers, les caractères fonctionnels sont désormais pris en compte. Actuellement, l’accent est mis sur la morphologie de la mamelle. La résistance à certaines maladies est à l’étude. Outre cette approche de génétique quantitative, de nouvelles perspectives basées sur une approche moléculaire permettront de détecter des gènes économiquement intéressants pour l’élevage caprin.
5
PAIVA, M. P., et M. F. ANDRADE-TUBINO. « Distribuição e abundância de peixes bentônicos explotados pelos linheiros ao largo do sudeste do Brasil (1986-1995) ». Revista Brasileira de Biologia 58, no 4 (novembre 1998) : 619–32. http://dx.doi.org/10.1590/s0034-71081998000400009.
Texte intégralRésumé :
Este trabalho trata da distribuição e abundância das principais espécies de peixes bentônicos explotados pelos linheiros ao largo do sudeste do Brasil (latitudes 18º-26ºS), no período 1986-1995, listadas a seguir, com as respectivas participações no total das capturas: batata = Lopholatilus vilariii Ribeiro = 33,4%, namorado = Pseudopercis numida Ribeiro = 18,4%, cherne = Epinephelus niveatus (Valenciennes) = 12,1%, garoupa = Epinephelus marginatus (Lowe) = 4,1% e badejo = Mycteroperca bonaci (Poey) = 3,1%. As pescarias ocorreram em águas tropicais (latitudes 18º- 23ºS) e subtropicais (latitudes 23º-26ºS), tendo como divisor zoogeográfico a ressurgência de Cabo Frio. Os dados foram agrupados por faixas de latitude e de profundidade, segundo espécies e estações do ano. As pescarias estiveram grandemente concentradas nas águas subtropicais, com tendência(s) de produtividade decrescente, à medida que aumenta(m) a latitude e/ou a profundidade dos pesqueiros explotados. Nas águas tropicais, as espécies dominantes foram a garoupa e o badejo, de forma indiscutível entre as latitudes 18º-20ºS, com maiores capturas em profundidades de até 80 metros. Nas águas subtropicais, as espécies dominantes sempre foram o batata, o namorado e o cherne, com maiores capturas em profundidades superiores a 100 metros, incluindo a parte superior do talude continental. A produção das cinco espécies principais apresentou tendências de variação estacional, mas apenas o cherne evidenciou deslocamento sazonal ao longo da costa. Foram comprovadas a menor diversidade e a maior biomassa de peixes bentônicos nas águas subtropicais.
6
Floyd, Matthew, Masaru Mizuyama, Masami Obuchi, Brigitte Sommer, Mark GR Miller, Iori Kawamura, Hiroki Kise, James D. Reimer et Maria Beger. « Functional diversity of reef molluscs along a tropical-to-temperate gradient ». Coral Reefs 39, no 5 (1 juillet 2020) : 1361–76. http://dx.doi.org/10.1007/s00338-020-01970-2.
Texte intégralRésumé :
Abstract Global warming is leading to range shifts of marine species, threatening the structure and functioning of ecological communities and human populations that rely on them. The largest changes are seen in biogeographic transition zones, such as subtropical reef communities, where species range shifts are already causing substantial community reorganisation. This causes functional changes in communities over subtropical latitudes, though a baseline functional understanding remains elusive for many taxa. One key marine taxon are molluscs, which provide many ecosystem services, are important prey for fishes and are also fisheries targets themselves, but remain largely unstudied. Here, we examine the trait composition, functional diversity, and functional redundancy of mollusc assemblages along the tropical-to-temperate transition in Japan (25° to 35° Northern latitude). Specifically, we use a trait database of 88 mollusc species from 31 subtropical reefs along the Pacific coast of Japan to show that trait composition of mollusc assemblages changes continuously along the latitudinal gradient. We discover that functional diversity of mollusc assemblages decreases with increasing latitude, a pattern associated with declines in functional dispersion. Moreover, we find a clear distinction between tropical and subtropical mollusc assemblages, with substrate-attached, suspension feeding bivalves more abundant in the tropics and free-living gastropod grazers more prevalent at higher latitudes. Our trait-based evidence in this study shows a contraction and almost complete shift in the functioning of marine mollusc assemblages at biogeographic transition zones and our trait database facilitates further study. Our findings provide evidence of the changing taxonomic and functional composition of extant mollusc communities with latitude, pointing to potential pertinent changes and tropicalisation of these communities with rapid ocean warming.
7
Bosmans, J. H. C., F. J. Hilgen, E. Tuenter et L. J. Lourens. « Obliquity forcing of low-latitude climate ». Climate of the Past 11, no 10 (9 octobre 2015) : 1335–46. http://dx.doi.org/10.5194/cp-11-1335-2015.
Texte intégralRésumé :
Abstract. The influence of obliquity, the tilt of the Earth's rotational axis, on incoming solar radiation at low latitudes is small, yet many tropical and subtropical palaeoclimate records reveal a clear obliquity signal. Several mechanisms have been proposed to explain this signal, such as the remote influence of high-latitude glacials, the remote effect of insolation changes at mid- to high latitudes independent of glacial cyclicity, shifts in the latitudinal extent of the tropics, and changes in latitudinal insolation gradients. Using a sophisticated coupled ocean–atmosphere global climate model, EC-Earth, without dynamical ice sheets, we performed two idealized experiments of obliquity extremes. Our results show that obliquity-induced changes in tropical climate can occur without high-latitude ice sheet fluctuations. Furthermore, the tropical circulation changes are consistent with obliquity-induced changes in the cross-equatorial insolation gradient, suggesting that this gradient may be used to explain obliquity signals in low-latitude palaeoclimate records instead of the classical 65° N summer insolation curve.
8
Bosmans, J. H. C., F. J. Hilgen, E. Tuenter et L. J. Lourens. « Obliquity forcing of low-latitude climate ». Climate of the Past Discussions 11, no 1 (11 février 2015) : 221–41. http://dx.doi.org/10.5194/cpd-11-221-2015.
Texte intégralRésumé :
Abstract. The influence of obliquity, the tilt of the Earth's rotational axis, on incoming solar radiation at low latitudes is small, yet many tropical and subtropical paleoclimate records reveal a clear obliquity signal. Several mechanisms have been proposed to explain this signal, such as the remote influence of high-latitude glacials, the remote effect of insolation changes at mid- to high latitudes independent of glacial cyclicity, shifts in the latitudinal extent of the tropics, and changes in latitudinal insolation gradients. Using a sophisticated coupled ocean–atmosphere global climate model, EC-Earth, without dynamical ice sheets, we performed two experiments of obliquity extremes. Our results show that obliquity-induced changes in tropical climate can occur without high-latitude ice sheet fluctuations. Furthermore, the tropical circulation changes are consistent with obliquity-induced changes in the cross-equatorial insolation gradient, implying that this gradient may be used to explain obliquity signals in low-latitude paleoclimate records instead of the classic 65° N summer insolation curve.
9
Upchurch, Garland R. « Cretaceous vegetational change : a biomal perspective ». Paleontological Society Special Publications 6 (1992) : 295. http://dx.doi.org/10.1017/s2475262200008558.
Texte intégralRésumé :
The Cretaceous rise of flowering plants marked an important transition in the modernization of terrestrial ecosystems. Well documented is the diversification of angiosperm pollen during the mid-Cretaceous and the migration of angiosperms from low latitudes to middle and high latitudes during the Barremian to Cenomanian. Global compilations of “species” diversity indicate a rapid rise in angiosperm diversity during the Albian to Cenomanian. This rise parallels a decline in the species diversity of archaic pteridophytes and the gymnosperm orders Cycadales, Bennettitales, Ginkgoales, Czekanowskiales, and Caytoniales. Late Cretaceous floras show more gradual trends in species diversity than mid-Cretaceous floras.Megafloral reconstructions of vegetation and climate for North America and other continents indicate warm temperatures in coastal regions of middle to high latitudes. Cretaceous biomes, however, often cannot be compared closely with Recent biomes. During much of the Cretaceous, conifers and other gymnosperms shared dominance with angiosperms in tropical and subtropical vegetation, unlike the Recent. During the Late Cretaceous, tropical rainforest was areally restricted. The few known leaf megafloras from equatorial regions indicate subhumid, rather than rainforest, conditions. Desert and semi-desert were widespread at lower latitudes and are documented by the occurrence of evaporite minerals in China, Africa, Spain, Mexico, and South America. Mid-latitude vegetation consisted of open-canopy broadleaved and coniferous evergreen woodlands that existed under subhumid conditions and low seasonality. High-latitude vegetation of the Northern Hemisphere consisted of coniferous and broadleaved deciduous forest, rather than boreal forest and tundra. High-latitude vegetation from coastal regions of the Southern Hemisphere consisted of evergreen conifers and angiosperms. Rainforest conditions appear to have been largely restricted to polar latitudes.Data on relative abundance, though often incomplete, indicate that angiosperms became ecologically important in tropical to warm subtropical broadleaved evergreen forests and woodlands by the Cenomanian. However, their rise to dominance took longer in other biomes. Conifers formed an important component of many Late Cretaceous biomes, and the persistence of archaic gymnosperms was strongly influenced by climate. Deciduous Ginkgoales, Czekanowskiales, Bennettitales, and Caytoniales are rare to absent in Late Cretaceous megafloras from warm subtropical to tropical climates, but they persist in megafloras from cooler climates. Archaic conifers such as Frenelopsis occur in megafloras representing low-latitude desert and semi-desert, but they are generally absent in more humid assemblages. Within mid-latitude broadleaved and coniferous evergreen woodland from North America, conifers show evidence for co-dominance with angiosperms into the early Maastrichtian. However, this co-dominance appears to have ended by latest Maastrichtian, which implies that vegetational reorganization occurred during the last few million years of the Cretaceous in North America.
10
Chen, Gang, et Pablo Zurita-Gotor. « The Tropospheric Jet Response to Prescribed Zonal Forcing in an Idealized Atmospheric Model ». Journal of the Atmospheric Sciences 65, no 7 (1 juillet 2008) : 2254–71. http://dx.doi.org/10.1175/2007jas2589.1.
Texte intégralRésumé :
Abstract This paper explores the tropospheric jet shift to a prescribed zonal torque in an idealized dry atmospheric model with high stratospheric resolution. The jet moves in opposite directions for torques on the jet’s equatorward and poleward flanks in the troposphere. This can be explained by considering how the critical latitudes for wave activity absorption change, where the eastward propagation speed of eddies equals the background zonal mean zonal wind. While the increased zonal winds in the subtropics allow the midlatitude eddies to propagate farther into the tropics and result in the equatorward shift in the critical latitudes, the increased winds in the midlatitudes accelerate the eastward eddy phase speeds and lead to the poleward shift in the critical latitudes. In contrast, the jet moves poleward when a westerly torque is placed in the extratropical stratosphere irrespective of the forcing latitude. The downward penetration of zonal winds to the troposphere displays a poleward slope for the subtropical torque, an equatorward slope for the high-latitude torque, and less tilting for the midlatitude torques. The stratospheric eddies play a key role in transferring zonal wind anomalies downward into the troposphere. It is argued that these stratospheric zonal wind anomalies can affect the tropospheric jet by altering the eastward propagation of tropospheric eddies. Additionally, the zonal wind response to a subtropical zonal torque in this idealized model is of value in understanding the tropospheric jet sensitivity to the orographic gravity wave drag parameterization in a realistic climate model.
Thèses sur le sujet "Latitudes subtropicales"
1
Carré, Aline. « Echanges stratosphère-troposphère durant la campagne PICO3 ». Toulouse 3, 2005. http://www.theses.fr/2005TOU30157.
Texte intégralRésumé :
Les intrusions stratosphériques jouent un rôle clé dans le bilan de l'O3 et sont associées à une grande incertitude. La bande subtropicale est une zone peu documentée, et les études climatologiques des déferlements des ondes de Rossby suggèrent que la filamentation des thalwegs d'altitude est un processus important d'intrusion stratosphérique dans cette région. Dans cette étude, je me suis intéressée à ce type d'intrusions liées à un épisode de déferlement d'une onde barocline des latitudes moyennes et de son interaction avec le jet subtropical. Le travail s'appuie sur la campagne PICO3 réalisée en octobre 2000 : le Mystère 20 de l'INSU, équipé pour la mesure d'03 (in-situ et télédétectée), a effectué plusieurs vols dans des filaments stratosphériques au-dessus des Iles Canaries. Par confrontation avec ces observations, l'utilisation de techniques lagrangiennes et de simulations numériques a permis d'analyser les processus de formation de ces filaments et d'évaluer leur impact vis-à-vis du transport S-T irréversibleStratospheric intrusions play a key role in the ozone budget and are still associated with incertitudes at global scale. Subtropical latitudes are poorly documented, and climatological strudies of Rossby Wave Breaking (RWB) suggest that it could be an important process leading to stratospheric intrusions into the subtropical troposphere. This study focuses on an episode of RWB over mid-latitude and its interaction with the subtropical jet. The case study is documented by the airborne campaign PICO3 which occurred on October 2000 : the INSU Mystere 20 aircraft was equipped with in-situ instruments of ozone and Lidar ALTO from the Service d'Aéronomie, and it sampled stratospheric filaments several times. By comparison between the airborne observations, the data from Lagrangian techniques and numerical simulations from a mesoscale model (Meso-NH), this study analyses the formation processes of these filaments and estimate their impact in term of irreversible or not stratosphere-troposphere transport
2
Silva, Adma Raia. « Ondas orográficas sobre a Cordilheira dos Andes em latitudes subtropical : estudo de caso ». Instituto Nacional de Pesquisas Espaciais (INPE), 2002. http://urlib.net/sid.inpe.br/jeferson/2004/05.27.09.45.
Texte intégralRésumé :
Uma variedade de fenômenos meteorológicos pode ser gerada ou modificada pelas montanhas. O conhecimento do escoamento sobre regiões montanhosas é um fator importante para se obter uma boa previsão de tempo. Na América do Sul poucos estudos foram realizados neste sentido. Este trabalho tem o objetivo de descrever o escoamento próximo aos Andes em situações relacionadas com os ventos tipo "foehn" (denominados localmente como "Zonda" na Argentina e "Raco" no Chile), e avaliar a necessidade de inserir uma parametrização de arrasto de ondas de gravidade no modelo Eta. As condições atmosféricas durante os eventos foram estudadas através de simulações com o modelo regional Eta e dados observados obtidos das estações meteorológicas disponíveis. O escoamento foi analisado através do parâmetro de "Scorer" e do número de Froude. Enquanto a instabilidade foi estudada através da energia cinética turbulenta e do número de Richardson. Dois casos foram estudados: um de Zonda ocorrido no dia 05 de agosto de 1999, e um de Raco, ocorrido no dia 05 de junho de 1999. Durante a ocorrência do Zonda um centro de baixa pressão atua a sotavento, isto é, sobre o noroeste da Argentina, e altas pressões do lado chileno, o padrão inverso ocorre durante o Raco. Os resultados mostraram que o modelo apresenta consistência nos processos físicos e indica a ocorrência de ambos fenômenos e suas características. As simulações concordaram melhor com a teoria do que com os campos de análise do NCEP. A propagação da onda na vertical foi claramente mostrada pelo parâmetro de "Scorer" no evento Zonda. As características do escoamento são mais marcantes no caso Zonda do que no Raco. Os erros sistemáticos identificados indicam a necessidade de inserir uma parametrização de arrasto de ondas de gravidade com o objetivo de minimizá-los. Na tentativa de minimizar os erros sistemáticos nas simulações dos fenômenos estudados, foi realizado um experimento aumentando o comprimento da rugosidade efetiva, e concluiu-se que a alteração deste parâmetro não é suficiente para ocorrer melhoria. Um esquema simples unidimensional de arrasto de ondas de gravidade foi testado, porém os resultados obtidos mostraram que o esquema é instável devido a forte dependência com o número de Richardson, que em determinadas condições atmosféricas assume valores irreais.A variety of meteorological phenomena can be generated or modified by the mountains. The knowledge of the flow on mountainous areas is an factor important to obtain a good forecast weather. In South America few studies were accomplished in this sense. This work has the objective to describe the flow in the vicinity the mountains in of situations related with the generation of the Zonda and Raco winds, and to evaluate the need to insert a parametrization of gravity waves drag in the Eta model. The atmospheric conditions during the events were studied through the simulations of the regional Eta model and observational data obtained from the available meteorological stations. The flow was studied through of the Scorer parameter and the Froude number. The instability of the flow was described by the turbulent cinetic energy and Richardson number. Two cases were studied in 1999: the Zonda wind case of august 05 and the Raco case of june 05. During the occurrence of Zonda a center of low pressure acts to the leeside, that is, in the northwest of Argentina, and high pressure center on the chilean side, the inverse pressure pattern has observed during Raco. The results showed that the model is consistent in the physical processes and indicated the occurrence of the phenomena and their characteristics. The results showed that the simulations agree better with the theory than with the analysis fields. The model systematic erros indicated the need to insert a parametrization of gravity waves drag in order to minimize those erros. An experiment was carried out to increase the effective roughness length. The results showed that the change in the roughness length is not enough to improve the simulations of the studied phenomena. A simple unidimensional gravity wave drag scheme was tested. The scheme removes the instability, but show large sensibility to Richardson number. A study of more complex parametrizationsis suggested in order to improve the weather forecast produced by Eta model.
3
Oliveira, Fernanda Marcello de. « Changes in the South Atlantic Subtropical Gyre circulation from the 20th into the 21st century ». Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/21/21135/tde-09042018-125458/.
Texte intégralRésumé :
Through analysis of large-scale ocean gyre dynamics from simulation results of the ocean component of the Community Earth System Model version 1 - the Parallel Ocean Program version 2 (CESM1-POP2) - this study builds upon existing research suggesting recent changes in the circulation of global subtropical gyres with respect to the South Atlantic Ocean. Results all point to an increase in the total counterclockwise circulation and a southward displacement of the sub- tropical gyre system. The northern boundary of the South Atlantic Subtropical Gyre (SASG) is represented by the bifurcation of the southern branch of the South Equatorial Current (sSEC) into the North Brazil Undercurrent/Current (NBUC/NBC) to the north and the Brazil Current (BC) to the south. The sSEC Bifurcation Latitude (SBL) dictates the partition between waters flowing poleward and those flowing equatorward. Although a northward migration of the SBL would be expected with the gyre spin up and associated poleward transport increase, the SBL migrates southwards at a rate of 0.051o/yr, in conjunction to a substantial increase in the equatorward advection of waters within the sSEC-SBL-NBUC system, which is included in the upper-branch of the Atlantic Meridional Overturning Circulation.Através de análises da dinâmica de grande-escala do giro oceânico, proveniente dos resultados de simulação da componente oceânica do Community Earth System Model versão 1 - o Parallel Ocean Program versão 2 (CESM1-POP2) - este estudo se baseia em estudos prévios sugerindo mudanças recentes na circulação dos giros subtropicais globais, com respeito ao oceano Atlântico Sul. Os resultados apontam para uma intensificação da circulação anti-horária e um deslocamento para sul de todo o sistema do giro subtropical. A borda norte do Giro Subtropical do Atlântico Sul (GSAS) é representada pela bifurcação do ramo sul da Corrente Sul Equatorial (CSEs) em Subcorrente/Corrente Norte do Brasil (SCNB/CNB) para norte e Corrente do Brasil (CB) para sul. A Latitude da Bifurcação da CSEs (LBC) determina a partição entre as águas fluindo em direção ao pólo e aquelas fluindo em direção ao equador. Embora seja esperada uma migração para norte da LBC com a aceleração da circulação do giro e consequente aumento do transporte em direção ao pólo, a LBC migra para sul a uma taxa de 0.051o/ano. Esta migração ocorre em conjunto à um aumento substancial na advecção de águas em direção ao equador com o sistema CSEs-LBC-SCNB, o qual está incluso no ramo superior da Circulação de Revolvimento Meridional do Atlântico.
4
Gatti, Junior Pedro. « Efeitos espaço temporais da poluição pontual e não pontual em uma bacia hidrográfica subtropical : ecohidrologia como ferramenta de controle ». Universidade Federal de São Carlos, 2015. https://repositorio.ufscar.br/handle/ufscar/7223.
Texte intégralRésumé :
Submitted by Daniele Amaral (daniee_ni@hotmail.com) on 2016-09-14T20:55:19Z
No. of bitstreams: 1
TesePGJ.pdf: 2065946 bytes, checksum: 88cecd364b6c5b24ea99e24abd33e1d9 (MD5)Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-16T19:46:32Z (GMT) No. of bitstreams: 1 TesePGJ.pdf: 2065946 bytes, checksum: 88cecd364b6c5b24ea99e24abd33e1d9 (MD5)
Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-16T19:46:40Z (GMT) No. of bitstreams: 1 TesePGJ.pdf: 2065946 bytes, checksum: 88cecd364b6c5b24ea99e24abd33e1d9 (MD5)
Made available in DSpace on 2016-09-16T19:46:47Z (GMT). No. of bitstreams: 1 TesePGJ.pdf: 2065946 bytes, checksum: 88cecd364b6c5b24ea99e24abd33e1d9 (MD5) Previous issue date: 2015-07-27
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Contaminants are introduced into aquatic ecosystems, both from point and diffuse sources and usually are deposited in the sediments of lakes and reservoirs. The input of diffuse pollutants in the environment is of difficult control and identification, while the control of point sources is more efficient because they are easily identified. However, the frequent discharges of effluents, althought undergoing treatment, may change the input of elements and substances in a given region. The aim of this study was to assess the spatial-temporal influence of point and non-point source pollution on the characteristics of surface water and sediment in a watershed with well-marked seasons. In addition, concepts and attempts at ecosystems restoration in different regions were reviewed in order to understand the main drivers of abiotic-biotic regulation among watersheds and aquatic ecosystems, based on the principles of Ecohydrology. For this purpose, the concentrations of Cd, Cr, Fe, Ni, Zn, Pb, Al, Cu, Mn, Hg, As, Se, total phosphorus, total nitrogen and ions in water and sediment were examined. Furthermore, levels of metals (Al, Fe, Mn, Cu, Zn, Hg and As) in the sediment profile of stations under of the influence of different impact were evaluated. This study showed that the point source pollution promote a high load of contaminants in sediment, regardless of the season. Furthermore, the point pollution sources seem to be spatially and temporally the main cause of reservoir sediment chemical composition due its frequent effluent release. This study also indicates that, despite several biogeographical differences, hydrology seems to be the main factor that controls the primary and secondary production and sustainability in rivers and lakes (reservoirs). In conclusion, the hydrology in the tropics seems to decrease the expected effects of a higher temperature. Therefore, to increase resilience in tropical freshwaters integrated actions according to hydrological stages are highly recommended.
Contaminantes são introduzidos em ecossistemas aquáticos, a partir de fontes pontuais e difusas e geralmente são depositados nos sedimentos de lagos e reservatórios. A entrada de poluentes difusos no ambiente é de difícil controle e identificação, enquanto que o controle de fontes pontuais é mais eficiente, pois são facilmente identificados. No entanto, as frequentes descargas de efluentes, mesmo passando por tratamento, podem mudar a dinâmica de entrada de elementos e substâncias em uma região. O objetivo deste estudo foi avaliar a influência espaço-temporal de fontes de poluição pontual e não pontual nas características das águas superficiais e do sedimento de um reservatório (Lobo/Broa, SP) em uma bacia hidrográfica com estações climáticas bem definidas. Além disso, conceitos e tentativas de restauração em diferentes ecossistemas foram revisados com o objetivo de entender quais são os principais controladores da regulação abiótica-biótica entre bacias hidrográficas e ecossistemas aquáticos, com base nos princípios da Ecohidrologia. Para este propósito, as concentrações de Cd, Cr, Fe, Ni, Zn, Pb, Al, Cu, Mn, Hg, As, Se, fósforo total, nitrogênio total e íons na água e no sedimento foram examinadas. Além disso, os níveis de metais (Al, Fe, Mn, Cu, Zn, Hg e As) no perfil do sedimento de pontos amostrais sob influência de diferentes impactos foram avaliados. Este estudo mostrou que as fontes pontuais de poluição promovem uma alta carga de contaminantes nos sedimentos, independentemente da estação. Além disso, as fontes de poluição pontual parecem ser espacialmente e temporalmente as principais causa da composição química de sedimentos do reservatório por causa da frequente liberação de efluentes. Esse estudo também indica que, apesar de várias diferenças biogeográficas, a hidrologia parece ser o principal fator que controla a produção primária, secundária e a sustentabilidade em rios e lagos (reservatórios). Em conclusão, a hidrologia nos trópicos parece diminuir os efeitos esperados de uma temperatura mais elevada. Portanto, para aumentar a resiliência nas águas doces tropicais ações integradas de acordo com as fases hidrológicas são altamente recomendadas.
5
« Ondas orográficas sobre a Cordilheira dos Andes em latitudes subtropical : estudos de caso ». Tese, Arquivo URLib de Teses e Dissertações do INPE, 2002. http://bibdigital.sid.inpe.br/rep-/sid.inpe.br/jeferson/2004/05.27.09.45.
Texte intégral
6
Burkholder, Kristin Cashman. « Subtropical to Subpolar Lagrangian Pathways in the North Atlantic and Their Impact on High Latitude Property Fields ». Diss., 2011. http://hdl.handle.net/10161/5686.
Texte intégralRésumé :
In response to the differential heating of the earth, atmospheric and oceanic flows constantly act to carry surplus energy from low to high latitudes. In the ocean, this poleward energy flux occurs as part of the large scale meridional overturning circulation: warm, shallow waters are transported to high latitudes where they cool and sink, then follow subsurface pathways equatorward until they are once again upwelled to the surface and reheated. In the North Atlantic, the upper limb of this circulation has always been explained in simplistic terms: the Gulf Stream/North Atlantic Current system carries surface waters directly to high latitudes, resulting in elevated sea surface temperatures in the eastern subpolar gyre, and, because the prevailing winds sweeping across the Atlantic are warmed by these waters, anomalously warm temperatures in Western Europe. This view has long been supported by Eulerian measurements of North Atlantic sea surface temperature and surface velocities, which imply a direct and continuous transport of surface waters between the two gyres. However, though the importance of this redistribution of heat from low to high latitudes has been broadly recognized, few studies have focused on this transport within the Lagrangian frame.
The three studies included in this dissertation use data from the observational record and from a high resolution model of ocean circulation to re-examine our understanding of upper limb transport between the subtropical and subpolar gyres. Specifically, each chapter explores intergyre Lagrangian pathways and investigates the impact of those pathways on subpolar property fields. The findings from the studies suggest that intergyre transport pathways are primarily located beneath the surface and that subtropical surface waters are largely absent from the intergyre exchange process, a very different image of intergyre transport than that compiled from Eulerian data alone. As such, these studies also highlight the importance of including 3d Lagrangian information in examinations of transport pathways.
Dissertation
Livres sur le sujet "Latitudes subtropicales"
1
Dunlop, Storm. 6. Weather in the tropics. Oxford University Press, 2017. http://dx.doi.org/10.1093/actrade/9780199571314.003.0006.
Texte intégralRésumé :
‘Weather in the tropics’ considers the weather systems between the two subtropical anticyclones, lying at approximately latitudes 30 °N and S. The trade winds consist of air that flows out of the subtropical anticyclones towards the equatorial trough. They are strongest in the winter season, tending to weaken during the summer. The northern and southern hemisphere trade winds converge at the Intertropical Convergence Zone, whose position is variable. The South Pacific Convergence Zone is closely associated with the changes involved in the Walker Circulation and El Niño events. The convergence zones over the Indian Ocean show major changes in location during the northern summer, and these are related to seasonal monsoons.
2
Plusminus 20/40 Latitude : Sustainable Building Design in Tropical and Subtropical Regions. Edition Axel Menges, 2007.
Trouver le texte intégral
3
Clarke, Andrew. Torpor and hibernation. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780199551668.003.0011.
Texte intégralRésumé :
A diurnal (circadian) rhythm in body temperature is a widespread, and possibly universal, feature of endotherms. Some mammals and birds down-regulate their metabolic rate significantly by night, allowing their body temperature to drop sufficiently that they become inactive and enter torpor. Both the minimum temperature achieved and the duration of torpor are highly variable. Daily torpor is principally a response to reduced energy intake, and a drop in ambient temperature. Hibernation is essentially an extreme form of torpor. Small mammals hibernating at high latitudes have regular arousals during which they urinate and may feed. Bears hibernate with relatively high body temperature, and do not undergo arousal. Only one bird, the poorwill, is known to hibernate. Rewarming during arousal may be fuelled exclusively by metabolism (for example in small mammals in the Arctic) or with significant energy input from basking (for example in subtropical arid areas). The capacity for torpor appears to be an ancestral character in both mammals and birds, possibly related to the origin of endothermy in small species subject to marked diurnal and/or seasonal variation in body temperature. Both deep hibernation and strict endothermy are probably derived characteristics.
4
Cook, Kerry H. Climate Change Scenarios and African Climate Change. Oxford University Press, 2018. http://dx.doi.org/10.1093/acrefore/9780190228620.013.545.
Texte intégralRésumé :
Accurate projections of climate change under increasing atmospheric greenhouse gas levels are needed to evaluate the environmental cost of anthropogenic emissions, and to guide mitigation efforts. These projections are nowhere more important than Africa, with its high dependence on rain-fed agriculture and, in many regions, limited resources for adaptation. Climate models provide our best method for climate prediction but there are uncertainties in projections, especially on regional space scale. In Africa, limitations of observational networks add to this uncertainty since a crucial step in improving model projections is comparisons with observations. Exceeding uncertainties associated with climate model simulation are uncertainties due to projections of future emissions of CO2 and other greenhouse gases. Humanity’s choices in emissions pathways will have profound effects on climate, especially after the mid-century.The African Sahel is a transition zone characterized by strong meridional precipitation and temperature gradients. Over West Africa, the Sahel marks the northernmost extent of the West African monsoon system. The region’s climate is known to be sensitive to sea surface temperatures, both regional and global, as well as to land surface conditions. Increasing atmospheric greenhouse gases are already causing amplified warming over the Sahara Desert and, consequently, increased rainfall in parts of the Sahel. Climate model projections indicate that much of this increased rainfall will be delivered in the form of more intense storm systems.The complicated and highly regional precipitation regimes of East Africa present a challenge for climate modeling. Within roughly 5º of latitude of the equator, rainfall is delivered in two seasons—the long rains in the spring, and the short rains in the fall. Regional climate model projections suggest that the long rains will weaken under greenhouse gas forcing, and the short rains season will extend farther into the winter months. Observations indicate that the long rains are already weakening.Changes in seasonal rainfall over parts of subtropical southern Africa are observed, with repercussions and challenges for agriculture and water availability. Some elements of these observed changes are captured in model simulations of greenhouse gas-induced climate change, especially an early demise of the rainy season. The projected changes are quite regional, however, and more high-resolution study is needed. In addition, there has been very limited study of climate change in the Congo Basin and across northern Africa. Continued efforts to understand and predict climate using higher-resolution simulation must be sustained to better understand observed and projected changes in the physical processes that support African precipitation systems as well as the teleconnections that communicate remote forcings into the continent.
5
Benestad, Rasmus. Climate in the Barents Region. Oxford University Press, 2018. http://dx.doi.org/10.1093/acrefore/9780190228620.013.655.
Texte intégralRésumé :
The Barents Sea is a region of the Arctic Ocean named after one of its first known explorers (1594–1597), Willem Barentsz from the Netherlands, although there are accounts of earlier explorations: the Norwegian seafarer Ottar rounded the northern tip of Europe and explored the Barents and White Seas between 870 and 890 ce, a journey followed by a number of Norsemen; Pomors hunted seals and walruses in the region; and Novgorodian merchants engaged in the fur trade. These seafarers were probably the first to accumulate knowledge about the nature of sea ice in the Barents region; however, scientific expeditions and the exploration of the climate of the region had to wait until the invention and employment of scientific instruments such as the thermometer and barometer. Most of the early exploration involved mapping the land and the sea ice and making geographical observations. There were also many unsuccessful attempts to use the Northeast Passage to reach the Bering Strait. The first scientific expeditions involved F. P. Litke (1821±1824), P. K. Pakhtusov (1834±1835), A. K. Tsivol’ka (1837±1839), and Henrik Mohn (1876–1878), who recorded oceanographic, ice, and meteorological conditions.The scientific study of the Barents region and its climate has been spearheaded by a number of campaigns. There were four generations of the International Polar Year (IPY): 1882–1883, 1932–1933, 1957–1958, and 2007–2008. A British polar campaign was launched in July 1945 with Antarctic operations administered by the Colonial Office, renamed as the Falkland Islands Dependencies Survey (FIDS); it included a scientific bureau by 1950. It was rebranded as the British Antarctic Survey (BAS) in 1962 (British Antarctic Survey History leaflet). While BAS had its initial emphasis on the Antarctic, it has also been involved in science projects in the Barents region. The most dedicated mission to the Arctic and the Barents region has been the Arctic Monitoring and Assessment Programme (AMAP), which has commissioned a series of reports on the Arctic climate: the Arctic Climate Impact Assessment (ACIA) report, the Snow Water Ice and Permafrost in the Arctic (SWIPA) report, and the Adaptive Actions in a Changing Arctic (AACA) report.The climate of the Barents Sea is strongly influenced by the warm waters from the Norwegian current bringing heat from the subtropical North Atlantic. The region is 10°C–15°C warmer than the average temperature on the same latitude, and a large part of the Barents Sea is open water even in winter. It is roughly bounded by the Svalbard archipelago, northern Fennoscandia, the Kanin Peninsula, Kolguyev Island, Novaya Zemlya, and Franz Josef Land, and is a shallow ocean basin which constrains physical processes such as currents and convection. To the west, the Greenland Sea forms a buffer region with some of the strongest temperature gradients on earth between Iceland and Greenland. The combination of a strong temperature gradient and westerlies influences air pressure, wind patterns, and storm tracks. The strong temperature contrast between sea ice and open water in the northern part sets the stage for polar lows, as well as heat and moisture exchange between ocean and atmosphere. Glaciers on the Arctic islands generate icebergs, which may drift in the Barents Sea subject to wind and ocean currents.The land encircling the Barents Sea includes regions with permafrost and tundra. Precipitation comes mainly from synoptic storms and weather fronts; it falls as snow in the winter and rain in the summer. The land area is snow-covered in winter, and rivers in the region drain the rainwater and meltwater into the Barents Sea. Pronounced natural variations in the seasonal weather statistics can be linked to variations in the polar jet stream and Rossby waves, which result in a clustering of storm activity, blocking high-pressure systems. The Barents region is subject to rapid climate change due to a “polar amplification,” and observations from Svalbard suggest that the past warming trend ranks among the strongest recorded on earth. The regional change is reinforced by a number of feedback effects, such as receding sea-ice cover and influx of mild moist air from the south.
Chapitres de livres sur le sujet "Latitudes subtropicales"
1
Delgadillo, José A., Philippe Chemineau et Matthieu Keller. « Using Socio-Sexual Stimulations for Sustainable Goat Production Under Subtropical Latitudes ». Dans Sustainable Goat Production in Adverse Environments : Volume I, 89–99. Cham : Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-71855-2_6.
Texte intégral
2
Stawski, Clare. « Comparison of Variables of Torpor Between Populations of a Hibernating Subtropical/Tropical Bat at Different Latitudes ». Dans Living in a Seasonal World, 99–108. Berlin, Heidelberg : Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-28678-0_9.
Texte intégral
3
Sherratt, Thomas N., et David M. Wilkinson. « Why are the Tropics so Diverse ? » Dans Big Questions in Ecology and Evolution. Oxford University Press, 2009. http://dx.doi.org/10.1093/oso/9780199548606.003.0009.
Texte intégralRésumé :
Our opening quotation describes Charles Darwin’s first experience of tropical forest on 29 February 1832. He had been looking forward to this moment for several years. While completing his studies at the University of Cambridge he had read Alexander von Humboldt’s accounts of tropical natural history and resolved that he too must experience the luxuriant vegetation and diversity of tropical species at first hand. Initially, Darwin planned to visit the subtropical island of Tenerife; however, this plan was superseded by the opportunity to join H.M.S. Beagle’s circumnavigation of the Earth—to his great disappointment Darwin never did get to land on Tenerife, although he saw it from the sea as the Beagle passed close by. Since Darwin’s time we have learnt much about the nature of biological diversity, both in the tropics and at higher latitudes. In this chapter, we review current knowledge of tropical diversity and how it compares with diversity at higher latitudes, before going on to discuss the various explanations that have been put forward to explain why the tropics have so many species. Here we define the tropics as the area between the Tropic of Cancer (23°28´ N) and the Tropic of Capricorn (23°28´ S) when we are discussing the modern world. In discussions of past climates, we refer to areas as ‘tropical’ if their reconstructed climates are similar to those currently experienced in the modern tropics. While we describe below how diversity changes with latitude, it is obvious that latitude itself is only part of a grid system that allows us to define the location of a point on the Earth’s surface, so it cannot itself have a direct effect on the number of species. However, many variables such as climate and land or ocean area are correlated with latitude and may provide an explanation for tropical diversity. Indeed, latitude itself is defined by the rotation of the Earth about its axis—a fundamentally abiotic (i.e. non-biological) planetary event. It follows that the ultimate cause of the gradient in diversity over latitude must be attributable to abiotic factors that are correlated with latitude, even if biological factors subsequently play a role in maintaining or promoting this diversity.
4
Pielke, Roger A., et Nolan J. Doesken. « Climate of the Shortgrass Steppe ». Dans Ecology of the Shortgrass Steppe. Oxford University Press, 2008. http://dx.doi.org/10.1093/oso/9780195135824.003.0006.
Texte intégralRésumé :
The climate of a region involves the short- and long-term interaction among the atmospheric, hydrologic, ecologic, oceanographic, and cryospheric components of the earth’s environmental system (Hayden, 1998; Pielke, 1998, 20 01a,b). These interactions occur across a ll spatial and temporal scales, from turbulence generated by diurnal cycles at a landscape scale, to globalscale circulation. The establishment of particular ecosystem types is associated with a nonlinear feedback between the atmosphere and the underlying vegetation (Pielke a nd Vidale, 1995). Wang a nd E ltahir (20 0 0) and Claussen (1998) have demonstrated that vegetation patterning cannot be accurately simulated in a model unless vegetation–atmosphere feedbacks are included. In this chapter we summarize the climate system of the shortgrass steppe. This is a region of large seasonal contrasts, and of interannual and longer term variability. It is also a region that has undergone major human impacts during the past 150 years. We present both average conditions and examples of extreme events in the shortgrass steppe to illustrate the variable climate of this interesting ecosystem. Geographic factors play a large role in determining the climatic characteristics of the shortgrass steppe (Lauenroth and Burke, 1995; Lauenroth and Milchunas, 1992; Lauenroth et al., 1999). Key factors for this region include its mid-latitude position, its relatively high elevations, its interior continental location, and its proximity to the Rocky Mountains, a substantial north–south-oriented mountain barrier immediately to the west. Air masses affecting the region consist of continental polar air from the north, humid continental air masses from the east, humid subtropical air masses from the southeast and south, and Paci8 c maritime air masses from the west. The latter can be signi8 cantly modi8 ed as they cross a series of mountain ranges and interior dry regions before reaching the shortgrass steppe region. Each of these geographic and atmospheric features contributes to the climate of the region. Latitude determines day length and sun angle, and, hence, solar insolation. This, in turn, greatly affects air temperature. Upper level westerly winds increase over the mid-latitudes in the fall and winter in response to strengthening north–south temperature gradients in the atmosphere. Paci8 c air masses are carried eastward over the Rocky Mountains, depositing considerable cool-season precipitation in the mountains, but rarely on the shortgrass steppe.
5
Worm, Boris, et Derek P. Tittensor. « Observed Patterns of Global Biodiversity ». Dans A Theory of Global Biodiversity (MPB-60), 10–53. Princeton University Press, 2018. http://dx.doi.org/10.23943/princeton/9780691154831.003.0002.
Texte intégralRésumé :
This chapter summarizes and synthesizes known biodiversity patterns, and analyzes them for congruency over space and time. The discussion is limited to macroecological patterns at continental to global scales (thousands of km). The chapter also focuses on the simplest measure of biodiversity—namely, species richness. The discussions cover marine coastal biodiversity, marine pelagic biodiversity, deep-sea biodiversity, terrestrial biodiversity, changes in biodiversity patterns through time, and robustness of documented biodiversity patterns. Among the findings is that averaging across all known species groups on land and in the sea, tropical peaks in species richness were as common as subtropical peaks, whereas species groups cresting in temperate or polar latitudes were more exceptional. Thus, the oft-cited unimodal pattern of biodiversity appears frequently, particularly on land, but there is also evidence that supports a newly emerging paradigm of asymmetric unimodal or bimodal peaks often in the subtropics, and particularly in the marine realm.
6
Garreaud, René D., et Patricio Aceituno. « Atmospheric Circulation and Climatic Variability ». Dans The Physical Geography of South America. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195313413.003.0010.
Texte intégralRésumé :
Regional variations in South America’s weather and climate reflect the atmospheric circulation over the continent and adjacent oceans, involving mean climatic conditions and regular cycles, as well as their variability on timescales ranging from less than a few months to longer than a year. Rather than surveying mean climatic conditions and variability over different parts of South America, as provided by Schwerdtfeger and Landsberg (1976) and Hobbs et al. (1998), this chapter presents a physical understanding of the atmospheric phenomena and precipitation patterns that explain the continent’s weather and climate. These atmospheric phenomena are strongly affected by the topographic features and vegetation patterns over the continent, as well as by the slowly varying boundary conditions provided by the adjacent oceans. The diverse patterns of weather, climate, and climatic variability over South America, including tropical, subtropical, and midlatitude features, arise from the long meridional span of the continent, from north of the equator south to 55°S. The Andes cordillera, running continuously along the west coast of the continent, reaches elevations in excess of 4 km from the equator to about 40°S and, therefore, represents a formidable obstacle for tropospheric flow. As shown later, the Andes not only acts as a “climatic wall” with dry conditions to the west and moist conditions to the east in the subtropics (the pattern is reversed in midlatitudes), but it also fosters tropical-extratropical interactions, especially along its eastern side. The Brazilian plateau also tends to block the low-level circulation over subtropical South America. Another important feature is the large area of continental landmass at low latitudes (10°N–20°S), conducive to the development of intense convective activity that supports the world’s largest rain forest in the Amazon basin. The El Niño–Southern Oscillation phenomenon, rooted in the ocean-atmosphere system of the tropical Pacific, has a direct strong influence over most of tropical and subtropical South America. Similarly, sea surface temperature anomalies over the Atlantic Ocean have a profound impact on the climate and weather along the eastern coast of the continent. In this section we describe the long-term annual and monthly mean fields of several meteorological variables.
7
Harding, Andrew, et Jean Palutikof. « The Climate System ». Dans The Physical Geography of the Mediterranean. Oxford University Press, 2009. http://dx.doi.org/10.1093/oso/9780199268030.003.0013.
Texte intégralRésumé :
The Mediterranean region has a highly distinctive climate due to its position between 30 and 45°N to the west of the Euro-Asian landmass. With respect to the global atmospheric system, it lies between subtropical high pressure systems to the south, and westerly wind belts to the north. In winter, as these systems move equatorward, the Mediterranean basin lies under the influence of, and is exposed to, the westerly wind belt, and the weather is wet and mild. In the summer, as shown in Figure 3.1, the Mediterranean lies under subtropical high pressure systems, and conditions are hot and dry, with an absolute drought that may persist for more than two or three months in drier regions. Climates such as this are relatively rare, and the Mediterranean shares its winter wet/summer dry conditions with locations as distant as central Chile, the southern tip of Cape Province in South Africa, southwest Australia in the Southern Hemisphere, and central California in the Northern Hemisphere. All have in common their mid-latitude position, between subtropical high pressure systems and westerly wind belts. They all lie on the westerly side of continents so that, in winter, when the westerly wind belts dominate over their locations, they are exposed to rain-bearing winds. In the Köppen classification (Köppen 1936), these climates are known as Mediterranean (Type Cs, which is subdivided in turn into maritime Csb and continental Csa). The influence of the Mediterranean Sea means that the Mediterranean-type climate of the region extends much further into the continental landmass than elsewhere, and is not restricted to a narrow ocean-facing strip. Nevertheless, within the Mediterranean region climate is modified by position and topographic influences can be important. The proximity of the western Mediterranean to the Atlantic Ocean gives its climate a maritime flavour, with higher rainfall and milder temperatures throughout the year. The eastern Mediterranean lies closer to the truly continental influences of central Europe and Asia. Its climate is drier, and temperatures are hotter in summer and colder in winter than in the west. Annual rainfall is typically around 750 mm in Rome, but only around 400 mm in Athens.
8
Rivadeneira, Marcelo M., et Gary C. B. Poore. « Latitudinal Gradient of Diversity of Marine Crustaceans : TOWARDS a Synthesis ». Dans Evolution and Biogeography, 389–412. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780190637842.003.0015.
Texte intégralRésumé :
The latitudinal diversity gradient (LDG) is a phenomenon acknowledged for over two centuries. The LDG of marine crustaceans has been studied often but without reaching consensus on its ultimate causative processes. We have undertaken a new synthesis to assess the generality of the LDG and evaluated how potential sampling and other biases, spatial scale, geographic regions, taxonomic aggregation, and differences between clades affect patterns. A meta-analysis of 186 datasets, encompassing 20 studies and 7 crustacean orders, revealed a strong effect size of the species richness-latitude correlation, supporting the existence of a “canonical” LDG. The effect size was sensitive to spatial scale, with studies conducted over shorter latitudinal ranges tending to show a weaker LDG. Correcting for sampling biases in the number of occurrences, taxonomic completeness and spatial heterogeneity did not affect the strength of the LDG, nor did the degree of taxonomic aggregation; effect sizes were similar at family and ordinal levels. However, between orders effect sizes varied strongly, with peracarid orders (Amphipoda, Cumacea, Isopoda) showing a weaker or inverse LDG compared with non-peracarid orders (Calanoida, Euphausiacea, Decapoda, Sessilia). Additional analyses based on a global dataset of >2 million occurrences of >13,000 species revealed patterns undetected by the meta-analysis, including: (1) the existence of a marked bi-modal LDG, with peaks of diversity in subtropical areas (Calanoidea, Decapoda, Sessilia) and in temperate areas (Amphipoda, Isopoda), (2) interhemispheric asymmetry, variable across groups and depths, and (3) ocean basin differences in the shape of the LDG, dependent on taxonomic clade. Both ecological and evolutionary processes play a part. The fossil record of Decapoda showed that its global canonical LDG can be explained by median and range of the age of genera, i.e., hotspots of diversity harbor both younger and older genera and contain a high proportion of genera originating during the Paleogene. In addition, the effect size was negatively related to family age, the LDG being stronger in older families of early Cenozoic and Mesozoic origin. Modes of larval development also played a significant part, taxa without planktonic larvae having weaker or inverse LDG compared with taxa with pelagic larvae. Because clades with direct development tend to show smaller bathymetric and latitudinal ranges than those with pelagic larvae, differences in diversification rates may be implied. Overall, our evidence suggested that the ultimate causes of the LDG are deeply tied to geographic differences in macro-evolutionary rates, i.e., greater rates of species origin and lower rates of extinction in the tropics than in higher latitudes combined with a strong tropical niche conservatism.
9
Bauer, Raymond T. « Life Cycle and Seasonal Migrations ». Dans Life Histories, 203–31. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780190620271.003.0008.
Texte intégralRésumé :
Seasonal and life cycle migrations are mass movements in which individuals move horizontally for long distances to encounter favorable conditions for reproduction and development. Such migrations have been best studied in larger mobile decapod crustaceans, many of which are commercially important. Some decapod shrimps and brachyuran crabs are dependent on productive estuaries for completion of life cycles. In these species, planktonic larvae develop in oceanic waters. Postlarval stages utilize currents and appropriate behaviors to enter estuaries via selective tidal stream transport (STST). After growth, juveniles and subadults leave for the adult oceanic habitats, again using STST. Many subtropical and temperate zone neritic species make seasonal offshore migrations into deeper waters during the winter, with return nearshore in the spring; some high latitude species make these migrations but with seasons reversed. Numerous freshwater shrimps are amphidromic, that is, they live and reproduce in streams and rivers, but their planktonic larvae drift or are released directly into the sea for development and dispersal. Postlarvae find the mouths of streams, and then make spectacular mass migrations as juveniles back upstream to the adult habitat. Adults of terrestrial crabs live inland, but brooding females move into the littoral zone during new or full moon periods to hatch out larvae into high amplitude tides that carry the larvae out to sea for development and dispersal.
10
Unganai, Leonard S. « Monitoring Agricultural Drought in Southern Africa ». Dans Monitoring and Predicting Agricultural Drought. Oxford University Press, 2005. http://dx.doi.org/10.1093/oso/9780195162349.003.0030.
Texte intégralRésumé :
Southern Africa lies between 0°S to 35°S latitude and 10°E to 41°E longitude. In this region, annual rainfall ranges from below 20 mm along the western coastal areas of Namibia to as high as 3000 mm in some highland areas of Malawi. Rainfall generally increases from south to north in response to topography and the main rain-bearing systems affecting the subregion. In the southwest sections of the sub-region, annual rainfall averages below 400 mm, whereas the high-altitude areas receive up to 3000 mm due to orographic enhancement. Two important features that control the climate of southern Africa are the semipermanent subtropical high-pressure cells centered in the southeast Atlantic and the southwest Indian Ocean. These subtropical high pressure cells are associated with widespread and persistent subsidence (Lockwood, 1979). Part of southern Africa is under the downward leg of the Hadley Cell, superposed on the zonal Walker cell. The complex interaction of these cells, particularly during warm El Niño/Southern Oscillation (ENSO) episodes, is usually associated with drier than normal austral summers over much of southern Africa. Much of southern Africa is therefore semiarid and prone to recurrent droughts. In South Africa, for operational purposes, a drought is broadly defined as occurring when the seasonal rainfall is 70% or less of the long-term average (Bruwer, 1990; Du Pisani, 1990). It becomes a disaster or severe drought when two or more consecutive rainfall seasons experience drought. Drought affects some part of southern Africa virtually every year. Southern Africa has suffered recurrent droughts since record keeping began (Nicholson, 1989; Unganai, 1993). Severe drought periods included 1800– 30, 1840–50, 1870–90, 1910–15, 1921–25, 1930–50, 1965–75, and 1980–95. During some of these drought periods, rivers, swamps, and wells dried up and well-watered plains turned into barren lands. For Zimbabwe, the worst drought years were 1911–12, 1923–24, 1946–47, 1972–73, 1981–82, 1982–83, 1986–87, and 1991–92 (Zimbabwe Department of Meteorological Services, personal communication, 2002). During the severe and recurrent droughts of the 1980s and 1990s, the impact on vulnerable communities and the environment was catastrophic.
Actes de conférences sur le sujet "Latitudes subtropicales"
1
Córdoba-Jabonero, Carmen, Eliane G. Larroza, Eduardo Landulfo, Walter M. Nakaema, Emilio Cuevas, Héctor Ochoa et Manuel Gil-Ojeda. « Active remote sensing observations for cirrus clouds profiling at subtropical and polar latitudes ». Dans SPIE Remote Sensing, sous la direction de Adolfo Comerón, Evgueni I. Kassianov, Klaus Schäfer, Richard H. Picard, Karin Stein et John D. Gonglewski. SPIE, 2014. http://dx.doi.org/10.1117/12.2067306.
Texte intégral
2
Fenerty, B., M. Bourne, J. Feinberg, J. Halligan et M. Waters. « INTEGRATED SURFACE DRAINAGE IN NORTHWEST FLORIDA'S KARSTIC GULF COASTAL LOWLANDS LINKED TO SHIFTING SUBTROPICAL STORM TRACKS IN RESPONSE TO HIGH-LATITUDE POST-GLACIAL CLIMATE CHANGE ». Dans GSA Annual Meeting in Seattle, Washington, USA - 2017. Geological Society of America, 2017. http://dx.doi.org/10.1130/abs/2017am-302871.
Texte intégral
3
Cardone, Vincent J., et Andrew T. Cox. « Modeling Very Extreme Sea States (VESS) in Real and Synthetic Design Level Storms ». Dans ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49731.
Texte intégralRésumé :
This paper addresses two questions critical for the successful real world application of the Cooperative Research on Extreme Seas and their Impact (CresT) Joint Industry Project (JIP) design methodology in harsh operating environments: (1) how accurately may very extreme sea states (VESS) be specified by modern numerical spectral wave models? About 20 storms in which VESS (defined as with significant wave height (HS) > 14 m) have been measured by various in-situ and satellite-mounted altimeters are hindcast and it is shown that when the meteorological forcing is accurately specified, a proven 3rd generation (3G) wave model provides skillful and unbiased specification of peak HS and by implication of the associated spectral properties. The second question addressed is: how do current 3G models behave when applied to even more extreme meteorological forcing than observed in the real storms studied? The same hindcast methodology is, therefore, applied to a population of synthetic hurricanes whose combinations of intensity and scale are predicted by deductive modeling studies of Gulf of Mexico hurricanes carried out following Hurricane Katrina (2004). The model results suggests that for a tropical cyclone to generate say peak HS > 20 m would require the peak wind intensity of a major hurricane (Category 3 or greater) combined with a larger size and faster translation speed than may be maintained by a tropical cyclone in tropical or subtropical settings. Large scale cyclonic and relatively rapidly translating storms with major hurricane force peak wind speeds indeed exist as a class of mid-latitude extratropical cyclones, dubbed “winter hurricanes”. Hundreds of such storms have been detected in global satellite altimeter data in virtually all major ocean basins. The peak sea states in the most extreme examples are also found to be simulated quite skillfully with the hindcast technology applied. The hindcast results are explored to infer the upper limit to the naturally occurring dynamic range of sea states in tropical and winter hurricanes.